Interspecific competition slows range expansion and shapes range boundaries

Area of Science:

• Ecology
• Evolutionary Biology
• Theoretical Ecology

Background:

• Species expanding into new habitats often encounter resident competitors, a phenomenon relevant to climate change and human introductions.
• Theoretical models predict that interspecific competition can influence expansion speed and range boundary shape, but experimental evidence is lacking.
• Current forecasting models for species expansion rarely incorporate competitive interactions due to this empirical gap.

Purpose of the Study:

• To experimentally demonstrate whether interspecific competition affects species range expansion speed and boundary shape.
• To investigate the long-term persistence of competitive effects on expansion dynamics.
• To inform ecological forecasting by incorporating species interactions.

Main Methods:

• Utilized a two-species experimental system with flour beetles (Tribolium castaneum and Tribolium confusum) to study interspecific competition during range expansion.
• Employed a parameterized stochastic model to analyze expansion dynamics over multiple generations.
• Observed and quantified changes in expansion speed and range boundary shape.

Main Results:

• Interspecific competition dramatically slowed the rate of range expansion across the experimental landscape over multiple generations.
• The shape of the expanding range boundary exhibited dynamic changes, initially steepening and then becoming shallower.
• Density-dependent dispersal of the invading species, coupled with resident competition, drove the observed boundary shape alterations.

Conclusions:

• Experimental evidence confirms that interspecific competition significantly impacts both the speed and boundary shape of species range expansions.
• The dynamic nature of range boundaries suggests that static assumptions in forecasting models can be misleading.
• Ecological models and management strategies for species expansions should integrate interspecific interactions for greater accuracy and effectiveness.